Exploration may play a crucial role in habitat choice by larvae of ben
thic organisms. Experiments testing exploratory behavior of larvae in
flow were conducted with cyphonautes larvae of the bryozoan Membranipo
ra membranacea. The response of the larvae to two flow parameters-flow
direction and shear (i.e., velocity)-was examined by using two differ
ent substratum morphologies (flat plate and cylinder), which induce di
stinct flow patterns. Settling cyphonautes larvae possess a mechanism
of locomotion, in addition to swimming, which may facilitate explorati
on in flow conditions that otherwise would sweep the larvae away. The
results show that cyphonautes larvae are able to explore substrata in
all directions in flow velocities that are much faster than their loco
motion speeds, and that their preferential motion is upstream. This be
havior has been largely ignored to date despite its potential ecologic
al importance. For instance, upstream exploration may enable larvae to
locate specific, obligatory settlement sites by tracking waterborne c
hemicals to their sources.